1. Field of the Invention
The invention relates to oxidation reactions in which epoxides are produced, and particularly relates to catalytic co-oxidations where an epoxide and a carboxylic acid are simultaneously produced from an olefin and an aldehyde, respectively.
2. Other Related Methods in the Field
It is known in the art to produce olefin oxides, especially ethylene oxide by reaction of the olefin in the vapor phase in the presence of silver catalysts. Various improvements have been made in this process including catalysts, reaction conditions and reactor design.
The direct oxidation of propylene to propylene oxide in the presence of silver catalysts is also known but the selectivity is low (50% at best), see Stanford Research Institute Report 2C, p. 259.
The direct liquid phase noncatalytic oxidation of propylene is also known in the art. The noncatalytic process results in low selectivity to the desired propylene oxide and a large number of co-products.
It is also known to oxidize propylene to propylene oxide in the presence of a catalyst. A high yield of epoxide is claimed using silica containing oxides of scandium, etc. as the catalyst (German Pat. No. 2,313,023). In this example, however, acetone is used as solvent and under these conditions acetone is consumed along with propylene.
U.S. Pat. No. 2,985,668 concerns the reaction of unsaturated compounds (including propylene) in the liquid phase (using high boiling solvents) in the presence of finely divided silver catalysts which were suspended in the liquid. Solvents claimed were mainly high boiling esters of carboxylic acids.
Most of the work concerning the silver catalyzed oxidation of olefins has been with ethylene and it is known that additives such as ethylene dichloride (EDC) and other chlorinated hydrocarbons retard the formation of by-products, see U.S. Pat. Nos. 2,279,469 and 2,734,906.
Co-oxidation procedures are also well known in the art. For example, the noncatalytic epoxidation of olefins by co-oxidation with secondary aliphatic aldehydes which are converted to the corresponding acids is taught by U.S. Pat. No. 3,265,716. The co-oxidation of propylene and p-tolualdehyde where water is used as a solvent is known, propylene glycol and p-toluic acid being the main products.
The kinetics and mechanics of the coupled oxidation of propylene and acetaldehyde are discussed in Bull. Acad. Sci. (USSR), vol. 8 (1966), p. 1283. The co-oxidation of benzaldehyde and cyclohexene in the presence of metal complexes containing platinum, rhodium, manganese, cobalt or molybdenum is described in another Russian article, see Chemical Abstracts 91:55955z (1979).
It is also known that propylene oxide and propylene glycol can be simultaneously produced by the oxidation of propylene over cobalt acetate according to Japanese Patent 80-021021. p-Tolualdehyde is also present, serving as a promoter, though it is also oxidized to the corresponding peracid.
The gas phase oxidation of acetaldehyde and propylene mixtures is reported as being an uneconomical process for the production of propylene oxide in Kogyo Kagaku Zasshi, vol. 69 (1966), p. 1863.
Methods for producing the acids alone are also known. For example, Japanese Patent 72-22,569 reveals that peroxy acids may be prepared by bubbling air into a solution of a benzaldehyde using a metal oxide such as mercury oxide, zinc oxide and cerium oxide as a catalyst. The preparation of carboxylic acids by oxidation of aldehydes with chloride is described in Acta. Chim. Scand., vol. 17 (1973), p. 880. Cobalt acetate is known to catalyze the oxidation of benzaldehyde according to Acta. Chim. (Budapest), vol. 78 (1973), p. 193.
U.S. Pat. No. 4,338,462 discloses a process for oxidizing methacrolein to methacrylic acid salt in the presence of oxygen and a strongly alkaline medium over a finely divided silver catalyst.
Of course, epoxidation of olefins is well known. German Pat. No. 3,002,811 discloses the epoxidation of cyclododecene or tricyclododecene with performic acid being generated "in situ" from hydrogen peroxide and formic acid. Epoxide production from olefins and hydrogen peroxide in an anhydrous solvent containing a boron catalyst according to German Pat. No. 2,952,755.
There is still a need for oxidation processes which provide a high yield to the epoxide. Preferably, such methods would employ a heterogeneous catalyst system.